The present invention relates to a variable speed drive unit and more particularly to a variable speed driving having a box type clutch for conveyor drives or the like having input and output shafts, a clutch disc stack including a first series of drive plates located in a fluid reservoir and supported for rotation by a rotatable housing rotated by one of the shafts and a second series of driven discs interleaved with the drive plates and supported for rotation with the other of the shafts, and a piston actuator slideably located at one end of the clutch disc stack and adapted to compressively engage the clutch disc stack.
Conventional variable speed drive units have a small clutch, a stepping motor, and a control panel controlling the stepping motor, the motor and control panel comprising approximately 75 percent of the cost of the unit. The present invention has the object of providing a variable speed drive unit which needs no back-up such as a costly stepping motor and control unit. Another object is to provide such a unit which provides a variable speed drive unit having a self-controlling drive profile without the need for electronic back-up or extraneous controls. A further object is to provide this drive profile as a ramp or having a gradually increasing rate profile.
Universality in use as a drive unit in various types of applications and simplicity in operation make a drive unit much more valuable in the art than a unit having only one specific application. Thus, it is yet another object of the present invention to provide the above objects in a universal and relatively simple to operate construction.
It is another object of the present invention to maintain a positive pressure in the oil system and particularly the interior chambers which comprise a large part of the volume of the oil system to facilitate the movement of the oil whether it is hot or cold.
In some applications, it is desirable to run the oil pump constantly to filter the oil whether the machine is down or in operation. A further object of the present invention is to permit the oil pump to run constantly, but also include an optional bypass around the heat exchanger to permit the use of a smaller heat exchanger for a selected oil pressure.
A further object is to provide the variable speed drive unit of the present invention having a centrifugal pump driving the oil and which can be interchangeably positioned with the heat exchanger. The position of the pump and heat exchanger would depend upon the position of the drive unit desired in the application utilized.
Other objects and advantages of the instant invention will be apparent in the following specification, claims and drawings.